Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
DHCP is a link-local broadcast protocol so AV:A (adjacent) is more accurate than AV:N; no auth or interaction needed (PR:N/UI:N) and memory corruption yields full C/I/A impact.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
6DescriptionNVD
Integer underflow (wrap or wraparound) in Windows DHCP Client allows an unauthorized attacker to elevate privileges over a network.
AnalysisAI
Privilege escalation in the Microsoft Windows DHCP Client service, driven by an integer underflow (CWE-191) triggered when processing DHCP traffic, lets an unauthorized network attacker gain elevated privileges with full confidentiality, integrity, and availability impact. It affects a broad Windows fleet spanning Windows 10 (1607/1809) and Windows Server 2012 through 2025, including Server Core installations. There is no public exploit identified at time of analysis and it is not in CISA KEV; EPSS is modest at 0.76% (51st percentile), but the vendor rates it critical (CVSS 9.8) and CISA SSVC flags it as Automatable.
Technical ContextAI
The flaw resides in the Windows DHCP Client component, which is responsible for obtaining IP configuration by exchanging DISCOVER/OFFER/REQUEST/ACK messages with a DHCP server and parsing the returned options (lengths, lease times, option payloads). CWE-191 (integer underflow/wraparound) means a length or size calculation on attacker-influenced DHCP fields drops below zero and wraps to a very large unsigned value, corrupting subsequent memory handling in the client. Per the CPE and EUVD data, the affected code ships across the Windows NT line: Windows 10 1607/1809 (10.0.14393 / 10.0.17763), Server 2012 and 2012 R2 (6.2.9200 / 6.3.9600), Server 2016 (10.0.14393), 2019 (10.0.17763), 2022 (10.0.20348), and 2025 (10.0.26100), including Server Core builds where the DHCP client is still present.
RemediationAI
Apply the Microsoft security update for CVE-2026-49181 from the MSRC advisory (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-49181); patch availability is confirmed by the vendor. Vendor-released patched builds are: Windows 10 1607 / Server 2016 to 10.0.14393.9339, Windows 10 1809 / Server 2019 to 10.0.17763.9020, Server 2012 to 6.2.9200.26226, Server 2012 R2 to 6.3.9600.23291, Server 2022 to 10.0.20348.5386, and Server 2025 to 10.0.26100.33158. Where immediate patching is not possible, compensating controls include enabling DHCP snooping and port security on managed switches to block rogue DHCP servers and constrain which hosts can answer DHCP on a segment (trade-off: requires switch support and careful trusted-port configuration or clients lose leases); segmenting/isolating untrusted devices off the same L2 broadcast domain as sensitive hosts (trade-off: network redesign effort); and, for statically-addressed servers that do not require DHCP, disabling the DHCP Client service (dhcp) (trade-off: breaks any dynamic addressing, DNS registration, and features that depend on the service, so validate before disabling). These are stopgaps - the update is the definitive fix.
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Same weakness CWE-191 – Integer Underflow
View allSame technique Authentication Bypass
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-43798
GHSA-7p5h-m8jh-5cmq